1. Technical Field
The invention relates to wheel end assemblies, and in particular to wheel end assemblies for heavy-duty vehicles, such as tractor-trailers. More particularly, the invention is directed to a hubcap of a wheel end assembly for a heavy-duty vehicle, which is connected to a wheel hub to seal the outboard end of the assembly, and includes an O-ring to provide improved sealing engagement with the hub, a lip and a shoulder that enable convenient alignment with the hub, an exterior cylindrical cavity that enables easy axial alignment of auxiliary devices, an opening that facilitates the mounting of components of a tire inflation system, and a step that improves impact resistance of the hubcap and the mounting of tire inflation system components.
2. Background Art
For many years, the heavy-duty vehicle industry has utilized wheel end assemblies which typically are mounted on each end of one or more non-drive axles. Each wheel end assembly typically includes a hub rotatably mounted on a bearing assembly that in turn is immovably mounted on the outboard end of the axle, commonly known as an axle spindle. As is well known to those skilled in the art, for normal operation of the wheel end assembly to occur, the bearing assembly and surrounding components must be lubricated with grease or oil. Therefore, the wheel end assembly must be sealed to prevent leakage of the lubricant, and also to prevent contaminants from entering the assembly, both of which could be detrimental to its performance. More specifically, a hubcap is mounted on an outboard end of the wheel hub, and a main seal is rotatably mounted on an inboard end of the hub and the bearing assembly in abutment with the axle spindle, resulting in a closed or sealed wheel end assembly.
While most wheel end assemblies include these general features, the design and arrangement of the hub, bearing assembly, hubcap, main seal, and other components, as well as the axle spindle, vary according to the specific vehicle design and its anticipated uses. For example, hubcaps of the prior art typically include a flat outboard surface, and a gasket that is disposed between a flange formed on the inboard end of the hubcap and the outboard surface of the hub to prevent bearing lubricant from leaking out of the wheel end assembly, and to prevent contaminants from entering the assembly. Such hubcaps, while adequate for some applications, include certain disadvantages.
For example, as mentioned above, the hubcap must provide an effective seal to prevent the bearing lubricant from leaking out of the outboard end of the wheel end assembly, and to prevent water and contaminants from entering the wheel end assembly. In the prior art, a gasket disposed between the hubcap and the outboard surface of the hub typically has been used to provide this seal. However, several potential issues may arise during reassembly after servicing of the wheel end assembly. For example, human error can result in failure to reinstall the gasket since it is a discrete component, and may thereby allow lubricant to leak out of the assembly, or may allow water and contaminants to enter the assembly. The gasket might also be under-tightened and may thus be loose, which could reduce the seal it provides and again potentially allow lubricant to leak out, or possibly allow water and contaminants to enter. The gasket could be over-tightened, which may crush it, again potentially reducing the seal it provides, which may allow lubricant to leak out, or may allow water and contaminants to enter. In addition, the gasket simply may degrade over time, potentially allowing lubricant to leak out of the wheel end assembly or potentially allowing water and contaminants to enter the assembly.
Moreover, the flat outboard surface of prior art hubcaps complicates the retrofit of devices that may be secured to the outboard end of the axle spindle and/or wheel end assembly. For example, a hub odometer is often attached to the hubcap. One type of hub odometer attaches to a prior art hubcap via a bracket, and for attachment uses the same bolts that attach the hubcap to the wheel hub. It is possible, during installation of the hub odometer, to overtighten these bolts in order to secure the bracket, which may crush the prior art gasket and cause it to leak.
Another type of hub odometer does not rely on bolts for attachment, and is secured directly to the hubcap. However, such odometers typically are installed on prior art hubcaps that threadably engage the wheel hub and are not intended by the manufacturer to be removed from the wheel hub. The flat outboard surface of the prior art hubcap, however, necessitates removal of the hubcap so that the axial center of the hubcap may be located and a hole drilled for the odometer. Since the seal between the hubcap and the wheel hub must be broken, lubricant may be lost and/or components may become contaminated.
In addition, devices used to measure axle alignment, such as a trammel bar or a wheel extender, typically are secured to the outboard end of the axle spindle and/or wheel end assembly and must be aligned with the axial centerline of the wheel end assembly near the outboard end of the axle spindle. The design of prior art hubcaps causes the users of some trammel bars and wheel extenders to remove the hubcap to align the trammel bar or the wheel extender, which could also result in undesirable loss and/or contamination of lubricant.
To overcome the disadvantage of a lack of an axial alignment point on prior art hubcaps having a flat outboard surface, other prior art hubcaps have been developed that include a dimple formed on the outboard surface of the hubcap. However, such hubcaps typically bolt onto the wheel hub, and the bolt holes of the hubcaps include bolt holes that are larger than the bolts, which can allow the hubcap to shift as it is installed. Thus, the dimple of such a prior art hubcap may not always be aligned with the axial centerline of the axle spindle and wheel end assembly.
Another disadvantage of prior art hubcaps is the potential for the hubcap to be subject to damage from impacts. More particularly, when an axle with a pair of wheel end assemblies is shipped from a manufacturer, the bearing assembly and hub of each wheel end assembly typically are installed on each respective axle spindle, without wheels or tires. The hubcap usually is assembled onto the hub, and without wheels in place, the hubcap extends outboardly past the remainder of the wheel end assembly. As the axle with the wheel end assemblies is prepared for shipment, loaded for shipment, and unloaded from shipment, the hubcaps thus are particularly susceptible to contact with other items and may undergo impacts, which is undesirable.
Prior art hubcaps required a significant number of bolts, such as six (6) or more, to enable the hubcap to maintain a sealed connection with the hub throughout such impacts. In addition, the straight-walled design of prior art hubcaps sometimes developed a crack under such impacts, requiring replacement of the hubcap. Moreover, the relatively large outer diameter of prior art hubcaps increased the possibility of contact with another object during transport, thereby increasing the potential that an impact might occur.
In addition, prior art hubcaps that are used with tire inflation systems include disadvantages associated with the mounting of components of the tire inflation systems. More particularly, tire inflation systems necessitate the mounting of additional components inside and/or proximate the hubcap, such as a rotary union assembly and air tubes. In order to mount such tire inflation system components, the hubcap typically must be removed from the wheel hub, but prior art hubcaps are designed to be sealed to the wheel hub and not removed, thereby undesirably making the component mounting process more complex and potentially problematic. Also, the relatively large outer diameter of prior art hubcaps often causes air tubes of a tire inflation system mounted on the hubcap to extend a significant distance in a radially outward direction, which may then cause a wheel to contact the air tubes when the wheel is removed from the hub for tire repair or replacement. Such contact with the air tubes may lead to damage of the tubes, or the need to remove the air tubes when the wheel is removed.
Moreover, prior art hubcaps lack the ability to accommodate the mounting of multiple separate components, which is inconvenient for some heavy-duty vehicle users. For example, components such as the rotary union assembly, which is mounted in an outboard end of the axle spindle, prevents centering of a trammel bar in the end of the axle spindle in certain prior art hubcaps. As a result, a heavy-duty vehicle user would have to remove the rotary union assembly to obtain a centering hole for the trammel bar, or would have to refrain from utilizing the trammel bar altogether. Therefore, such prior art hubcaps undesirably limit the components that may be installed or used on the axle spindle and the wheel end assembly.
These disadvantages of prior art hubcaps make it desirable to develop a hubcap for a heavy-duty wheel end assembly that provides a more effective seal, readily and accurately accommodates an odometer, a trammel bar or a wheel extender without disturbing the sealing connection between the hubcap and the wheel hub, resists damage from impacts, accommodates a protective plug, facilitates the mounting of certain tire inflation system components either alone or in combination with other components such as odometers, trammel bars, wheel extenders, and the like, and enables tire inflation system components to be mounted in a manner that allows a wheel to be easily removed without damage to the system components. The present invention satisfies these needs.